Process for treating rare earth-fluorine materials



Patented Nov. 21, 1967 3,353,928 PROCESS FGR TREATING RARE EARTH-FLUORINE MATERIALS Mark M. Woyski, La Habra, James L. Bradford, Anaheim, and Henry H. Elliott, Fullerton, Calif., assignors to American Potash & Chemical Corporation, Los Angeles, Calif., a corporation of Delaware- No Drawing. Filed Feb. 26, 1965, Ser. No. 435,745 11 Claims. (Cl. 23-318) ABSTRACT OF THE DISCLOSURE A process for the recovery of substantially all of the rare earth values from rare earth-fluorine materials, in particular fluocarbonate ores such as bastnasite. The ore material is chlorinated or brominated in the presence of a fluorine acceptor to convert the rare earth values to water-soluble rare earth chlorates or bromates.

The present invention relates to the treatment of rare earth-fluorine materials. More particularly, the present invention relates to procedures for converting the rare earth values in rare earth-fluorine compounds to rare earth chlorides, bromides or iodides.

The treatment of rare earth materials, and in particular, rare earth bearing ores by acid leaching procedures is known. Heretofore, such procedures have not been completely satisfactory when applied to rare earth fluocarbonate ores because it has not been possible to recover more than about 75 percent by weight of the contained rare earth values, based on the total weight of rare earth values present in the ore. The values which were not recoverable by prior art acid leaching techniques were found to be present in the ore as acid-insoluble rare earthfluorine compounds. Attempts to recover substantially 100 percent of the contained rare earth values, including the said acid-insoluble values, in a convenient and economical manner have been generally unsuccessful.

In accordance with the present invention, there is provided a process which results in the recovery of substantially all of the rare earth values from rare earth-fluorine materials, including at least the major portion of the heretofore unrecoverable rare earth values present as acid-insoluble rare earth-fluorine compounds.

It will be understood that the term rare earth as used in the present specification and appended claims includes: those elements of the lanthanide series having atomic numbers from 57 through 71, inclusive, and the elements thorium, yttrium and scandium which may be present in minor amounts in rare earth ores.

Broadly, the present invention provides a process for the recovery of rare earth values from rare earth-fluorine compounds, and in particular from rare earth fluocarbonate ores such as bastnasite ores, by subjecting the said compounds or ores, preferably while in particulate form, to chlorination or bromination in the presence of a fluorine acceptor. By this treatment, at least the major portion of the rare earth values present in the ore are converted to water-soluble rare earth halides.

If desired, the chlorination or bromination of the ore can be preceded by other ore-opening techniques including, for example, pyrolysis to drive ofl carbon dioxide and convert the rare earth fluocarbonates to rare earth oxyfluorides; leaching with dilute mineral acids to solubilize the alkaline earth carbonateprincipally calcium carbonate-portion of the ore; digesting with concentrated mineral acid to dissolve the acid-soluble rare earth values in the ore; or other techniques.

The term halogenation as used in this specification and in the claims appended hereto, unless otherwise defined, means: a reaction whereby the rare earth values in a. rare earth-fluorine compound are converted to watersoluble rare earth chlorides or bromides. Unless otherwise indicated, the term halogenation does not include a process whereby rare earth fluorides, iodides or rare earth astatides are produced.

Fluorine acceptors are compounds or elements which combine with the fluorine portion of the rare earthfluorine compounds to produce compounds of fluorine which are volatile at the reaction temperatures of this invention.

Fluorine acceptors may be supplied to the reaction zone as such, or they may be provided in admixture with, or as a part of, some other compound or composition. For purposes of differentiating the fluorine acceptors, as such, from compounds or compositions containing fluorine acceptors, such compounds and compositions are identified in this specification and in the appended claims as fluorine exchange agents. Illustrative examples of fluorine exchange agents include silicon'tetrachloride, silicon dioxide, boron trichloride and the like. Silicon and boron are the fluorine acceptors in these fluorine exchange agents.

The reaction mechanisms whereby the fluorine acceptors are released from the fluorine exchange agents and combined with the fluorine contained in the rare earthfluorine compounds are not now fully understood. In general, suitable fluorine exchange agents include those agents capable of releasing one or more of the fluorine acceptors boron, silicon, germanium, phosphorus, arsenic, antimony and the like at temperatures between about 450 C. and 800 C. The corresponding fluorides of these fluorine acceptors are volatile at temperatures below 800 C. The volatile compounds of fluorine are swept out of the reaction zone as they are formed along with the other gaseous reaction products. These volatile compounds of fluorine may be removed from the gas stream, for example, by washing the gas with water, dilute caustic or lime slurry.

Since the rare earth chlorides and bromides are not volatile at the temperatures prevailing in the reaction zone, a separation of the volatile fluoride, from the nonvolatile halide compounds is conveniently accomplished during the reaction.

When combined oxygen is present in the rare earthfluorine compound, such as is the case with rare earth fluocarbonate ores, and rare earth oxyfluorides, some oxy gen scavenger must be provided to remove the oxygen. Convenient oxygen scavengers are carbon and carbon monoxide.

As with the fluorine acceptors, oxygen scavengers may i be provided in the reaction zone by supplying such scavengers to that Zone in admixture with, or as a part of, some other compound or composition. For purposes of diflerentiating the oxygen scavengers, as such, from compounds 'or compositions containing oxygen scavengers, such compounds and compositions are identified in this specification and in the appended claims as oxygen scavenger agents. Illustrative examples of suitable oxy: gen scavenger agents include phosgene, carbon tetrachloride and the like. Carbon, carbon monoxide and mixtures thereof are the oxygen scavengers in these oxygen scavenger agents. In general, suitable oxygen scav-.

enger agents include those agents capable of releasing one or both of carbon or carbon monoxide at temperatures between about 450 C. and 800 C.

Suitable halogenating agents include those agents capable of releasing one or both of chlorine or bromine at temperatures between about 450 C. and 800 C. Illustrative examples of suitable halogenating agents include boron trichloride, phosgene and the like.

As with the fluorine acceptors, the reaction mechanisms whereby the chlorine or bromine is released from the halogen exchange agents and combined with the rare earth contained in rare earth fluorine compounds are not now fully understood.

Many compounds and com-positions are capable of serving more than one function when supplied to the reaction zone. For example, phosgene is both a halogenating agent and a oxygen scavenger agent. This is due to its disassociation into chlorine and carbon monoxide at the temperatures in the reaction zone. Boron trichloride is both a fluorine exchange agent and a halogenating agent.

The molar proportions of fluorine acceptors, chlorine or bromine and oxygen scavengers, if required, may be considerably varied, but ordinarily when complete conversion of all rare earth values to rare earth chlorides or bromides is desired it is necessary to provide at least stoichiometric amounts of fluorine acceptors and chlorine or bromine in the reaction zone. In order to prevent the conversion of the rare earth values to rare earth oxides, it is necessary to provide stoichiometric amounts of oxygen scavengers in the reaction zone.

The reactants may be supplied to the reaction zone at any desired rate. In general, only a small fraction of the stoichiometric amounts of the gaseous reactants will be present in the reaction zone at any one time. The reaction zone may be maintained under positive pressures to increase the concentration of the gaseous reactants in the reaction zone, if desired. It is not, however, necessary to resort to super-atmospheric pressures in the reaction zone in order to accomplish the halogenation reactions in this invention. Excesses of fluorine acceptor, oxygen scavenger and chlorine or bromine, several thousand times greater than the stoichiometric amounts of these materials are not detrimental, and may be used if desired. Unreacted gaseous reactants pass through the reaction zone and are generally collected for recycle.

Preferably the halogenation reactions of this invention are carried out in a substantially oxygen-free reaction zone. The exclusion of oxygen from the reaction zone prevents the rare earth values from being converted into water-insoluble rare earth oxides. Oxygen is conveniently excluded from the reaction zone by conventional techniques such as, for example, by sweeping the reaction zone with an inert gas such as helium or by applying a vacuum to the zone.

The rare earth chlorides and bromides produced by the process of this invention can be utilized as desired. For example, these rare earth halides may be dissolved in an aqueous solution to separate the rare earth values from the insoluble gangue. The rare earth-bearing solution may be separated from the gangue by filtration or other convenient means. Rare earth chlorides or bromides can be separated from the solution by conventional procedures, for example, by evaporation. The rare earth halide may be reduced to the rare earth metal. Rare earth metal may be alloyed with iron as a nodularizing agent. Alternatively, the rare earth halides may be converted to pure rare earth oxides which enjoy wide utility, for example, in glass polishing compositions. Individual rare earths may be separated from one another, for example by ion exchange.

Broadly, the rare earth fiuocarbonate ores to which this process can be applied are known to those skilled in the art to have the following approximate weight percentage compositions:

Percent Fluorine 0.1-9 Rare earths 0.3-8 Alkaline earth metal carbonates 0.1-75 Silica 0.1-25 Barium sulfate 4-50 Iron oxide 0.1-5 Aluminum oxide 0.1-5

The rare earth fluocarbonate ores to which the process of this invention is applicable include, for example, low grade run of the mine materials as well as concentrates produced by flotation, acid leaching, pyrolysis and other conventional beneficiation processes. Representative examples of ores, including their concentrates comprise those having the following approximate weight percentage compositions:

Rare earth fluocarbonate ores may be found in association with a wide variety of other minerals and valueless gangue materials, some of which may be carried with the fiuocarbonate ores into the present process. Such extraneous materials are not generally detrimental to the halogenation reactions.

The rare earth fluocarbonate ores can be subjected to conventional ore-dressing procedures prior to the application of halogenation procedures. Such conventional oredressing procedures include, for example, the separation of valueless gangue and other extraneous materials by such techniques as classification, flotation, sedimentation and the like.

The particle size of the rare earth fluocarbonate ore is not critical; however, it is generally possible to increase the rate of reaction by decreasing the particle size. If the particle size is too large, it is difficult to carry the reaction to completion in a reasonable length of time.

The ore, prior to being subjected to halogenation, preferably is treated to reduce its size such that it will pass a Number 3 US. Standard screen; the particles may be as small as 1 micron or less. Preferably, the particle size of the ore is such that it passes a mesh (US. Standard) screen. The particulate ore may be pelletized if desired. The conventional ore dressing, sizing and pelletizing operations can be accomplished on commercially available apparatus.

Halogenation of the rare earth fluocarbonate ore can be accomplished either continuously or batch-wise in commercially available equipment such as, for example, rotary kilns, furnaces, fluidized bed apparatus, and the like.

In general, the halogenation reactions of this invention may be carried out at any temperature at which rare earth chlorides or bromides are produced without sintering the reaction bed.

The halogenation reactions of this invention preferably are carried out while the rare earth-fluorine compound is maintained at a temperature between 450 C., and 800 C., preferably between about 550 C. and 750 C. At about 500 C., the reactions proceed rather slowly and may not go to completion, while at about 750 C., care must be taken to avoid fusing the reaction bed into a solid mass. The optimum temperature for the convenient halogenation of any given ore sample is dependent upon such variables as, for example, the composition of the ore, the particle size of the ore, the equipment used, the treatment of the ore prior to halogenation, and the like.

The time required to complete the halogenation reaction, using ore of a given particle size, is largely dependent upon temperature and is determined conveniently by analysis of the solid reaction products for water-insoluble rare earth values and fluorine content. When the reaction is complete substantially, all of the rare earth values will be water-soluble and the solid reaction products will contain little if any fluorine. In general, the halogenation reactions of this invention are complete in a period of time ranging from about 15 minutes to 12 hours.

The halogenation reaction may be applied to the rare earth containing insoluble residue remaining after treating the ore with concentrated acid.

Typical analytical procedures for the determination of rare earths may be found in Treatise on Analytical Chemistry, Kolthoff and Elving, Part II, vol. 8.

General methods for the determination of fluorine in bastiinsite are given in Treatise on Analytical Chemistry, Part II, vol. 7.

In the specification, claims and following specific examples. all parts and percentages are by weight unless otherwise indicated. The following examples are set forth to further illustrate and not to limit the invention.

Example I The bastniisite ore used in this example is that having the unleached composition shown in Example II, infra. This bastniisite ore concentrate is milled in a ball mill to a particle size of 325 mesh (US. Standard).

The apparatus used in this example consists of a 36-inch long quartz reaction tube having an inside diameter of l-inch. This tube is mounted vertically and a reaction mixture consisting of about 35 grams of 325 mesh bastniisite ore and about 55 grams of finely divided wood charcoal are supported in the central 9-inch section of the tube. This central 9-inch section comprises the reaction zone in which halogenation is carried out. This 9- inch section of the tube containing the reaction bed is centrally located inside an 18-inch long resistance heating element. Gaseous reactants are fed to the top of the reaction tube and the vaporized reaction products are removed from the bottom of the tube. The temperature of the bastniisite-charcoal reaction bed is monitored by a thermocouple inserted in the bed.

The reaction bed and the surrounding tube are heated to a temperature of about 700 C., while a stream of dry argon is passed through the tube to sweep the reaction zone free of oxygen. About 36 grams of phosgene and about 10 grams of a fluorine exchange agent consisting of silicon tetrachloride are added to the tube simultaneously at a uniform rate over about a 4-hour period. At this temperature the phosgene is almost completely disassociated into chlorine, which functions as the chlorinating agent, and carbon monoxide which functions as an oxygen scavenger. The vaporous reaction product contains silicon tetrafiuoride, carbon monoxide, carbon dioxide, traces of phosgene, traces of free chlorine, and toward the end of the reaction period, some silicon tetrachloride.

Analysis of the solid reaction product contained in the reaction bed shows that about 99.8 percent of the rare earth and thorium values in the original bastn'ztsite charge are converted to the corresponding chlorides. Fluoride analysis of the bed residue shows that the fluorine has been removed completely.

Repetition of this example, eliminating the silicon tetrachloride, results in a substantial decrease in the percent conversion of the rare earth values in the bastnasite ore to water soluble rare earth chlorides even though the reaction is carried out using about 81 grams of phosgene and about a 5-hour reaction period at approximately 700 C. This repeated example illustrates that the presence of the fluorine exchange agent, silicon tetrachloride, results in an increased yield of water soluble rare earth chlorides and a substantial decrease in both the amount of phosgene required and the reaction time. Since some silicon tetrafluoride is found in the gaseous reaction product produced in this repeated example, apparently small quantities of the fluo ine exchange agent, silicon tetrachloride, are formed by the interaction of phosgene with those silicon values occurring naturally in the bastnasite ore. Analysis of the solid bed residue formed in this reaction reveals that it still contains a considerable fluorine content.

Repetition of Example I, using a reaction temperature 6 of about 750 C., results in a substantial decrease in the reaction time.

Example [I This example illustrates the optional pre-treatment of rare earth ore with dilute mineral acid to dissolve and remove a portion of its original alkaline earth metal carbonate content.

A bastniisite ore concentrate, percent of which passes a 200 mesh sieve (US. Standard), is found to have the following composition:

Ore components: Weight percent 1 Ln is a generic symbol used to represent all of the rare earth elements generally. A mixture of rare earth oxides is present here.

@1203 is a generic symbol used to indicate those compounds which, during systematic analysis, are precipitated from solution by the addition of ammonium hydroxide and includes iron oxide, aluminum oxide and titanium oxide. Phosphorus pentoxide is co-precipitated with iron oxide and is included here.

A sample of this bastnasite ore composition is admixed With hydrochloric acid solution at ambient temperature. A sutticient quantity of hydrochloric acid solution is used to bring the pH of the mixture down to a constant value of about 1. The undissolved residue is washed twice by decantation, filtered and dried. This dried, leached residue of bastnasite ore c-oncentrate contains about 72.9 weight percent rare earth oxides, about 4.5 weight percent fluorine and has a loss on ignition of about 19.6 weight percent. The composition of the mineral bastn'asite can be represented by the formula LnFCO Using CaCO to represent the alkaline earth carbonates in general, the

principal reactions taking place during this dilute hydrochloric acid leach can be represented as follows:

LnFCO +dilute H-Cle substantially no reaction CaCO +dilute HC1+ CaC1 +H O+CO Example III This example is illustrative of the chlorination of rare earth-fluorine compounds using silicon dioxide as the fluorine exchange agent. The rare earth-fluorine compound used in this example is rare earth fluoride.

An intimate admixture containing about 4 grams of rare earth fluoride and about 0.9 gram of powdered silicon dioxide is placed in a silica boat and the boat is inserted in a combustion tube. The combustion tube is heated to a temperature of about 700 C. About a 19 gram quantity of phosgene is passed into the combustion tube at a uniform rate over about a 2-hour period. At the end of the reaction, analysis of the solid residue in the silica boat discloses that about 96 percent of the rare earth fluoride has been converted to the corresponding rare earth chloride.

Repetition of this example without the silicon dioxide results in only about a 4 percent conversion of the rare earth fluoride to the rare earth chloride. This repeated example, by contrast with Example III, shows the importance of using a fluorine exchange agent in the halogenation reaction.

Example IV This example is illustrative of the use of a mixture of phosphorus trichloride and phosphorus oxychloride as the fluorine exchange agent.

The procedures and conditions described in Example I, above, are repeated except that the silicon tetrachloride is replaced with a vaporized admixture containing about 12 grams of phosphorus trichloride and about 12 grams of phosphorus oxychloride. The phosgene and phosphorus trichloride-phosphorus oxychloride admixture is supplied to the reaction bed at a uniform rate over a period of about 4 hours. Better than 90 percent of the rare earth values in the ore are recovered from this reaction as water-soluble rare earth chlorides. Phosphorus trifluoride and phosphorus oxyfluoride are the major constituents in the exit gases.

Repetition of this example using phosphorus tribromide and phosphorus oxybrornide in place of the phosphorus trichloride-phosphorus oxychloride admixture, and elemental bromine in place of the chlorine results in a better than 90 percent conversion of the rare earth values to rare earth bromides.

Repetition of this example using a reaction temperature of about 500 C. results in a relatively slow rate of reaction.

Example V This example is illustrative of the use of boron trichloride as a combined chlorination and fluorine exchange agent.

About a 4.2 gram sample of rare earth fluoride is placed in a silica boat and the boat is inserted in a combustion tube. The combustion tube is heated to a temperature of about 700 C., and about 11 grams of boron trichloride are passed into contact with the contents of the boat at a uniform rate over about a 2-hour period. The presence of carbon or other oxygen removal agent is not required in this reaction mixture because the rare earth fluoride does not contain combined oxygen. The gaseous reaction product contains large amounts of boron trifluoride. Analysis of the residue in the boat shows about a 98 percent conversion of the rare earth fluoride to the corresponding rare earth chloride.

Example Vl Prior to halogenation the ore used in this example is digested with concentrated mineral acid. The digested bastnasite is chlorinated to recover those rare earth values which cannot be solubilized with mineral acids.

About a 100 gram sample of leached bastnasite ore concentrate prepared by the method of Example II, above, is subjected to attack by about 375 ml. of boiling 6 normal hydrochloric acid, under reflux, for about 4 hours. At the end of this 4 hour period, the insoluble residue is separated from the solution and dried. The residue weighs about 24.2 grams. Analysis shows it to contain about 66 percent rare earths as the oxides and about 19.2 percent fluorine.

The residue is subjected to chlorination, using the same procedure described in Example I, above, at a temperature of about 750 C., and a treatment time of about 2.5 hours.

The solid chlorination product is leached with 0.3 normal hydrochloric acid. Analysis of the solution so obtained from this leaching step discloses that substantially all of the rare earth values present in the insoluble residue prior to chlorination are dissolved in the leach solution.

Repetition of Example I, using Various fluorine exchange agents and halogenation agents gives the results indicated below. The substitution of silicon tetrabromide for silicon tetrachloride, and elemental bromine for phosgene, results in substantially quantitative yields of water soluble rare earth bromides. The substitution of arsenic trichloride and antimony trichloride, respectively, in two separate examples, for silicon tetrachloride in Example I, results in substantially quantitative yields of rare earth chlorides in each example. When arsenic tribromide and antimony tribromide are used in conjunction with elemental bromine very high yields of rare earth bromides are achieved. The substitution of elemental phosphorus for silicon tetrachloride, and elemental chloride for phosgene in a repetition of Example I, results in acceptable yields of rare earth chlorides. The substitution, in six separate examples of boron carbide, silicon carbide, boric oxide, phosphorus pentoxide, boron nitride and silicon nitride, respectively, for the silicon tetrachloride of Example I results in acceptable yields of rare earth chloride.

Repetition of Example I, using raw run-of-mine ore, results in excessive consumption of phosgene and silicon tetrachloride with the evolution of copious quantities of carbon dioxide.

As illustrated in the foregoing examples, a wide variety of fluorine exchange agents are suitable for use in the present invention. Suitable fluorine exchange agents include, for example, the oxides, nitrides, carbides, chlorides and bromides of silicon, boron, germanium, phosphorus, arsenic, and antimony, as well as elemental boron, silicon, phosphorus, arsenic and antimony and mixtures thereof.

Suitable halogenating agents for use in the process of this invention include elemental chlorine and bromine as well as phosgene, carbon tetrachloride, carbon tetrabromide, phosphorus tribromide, phosphorus oxybrornide, boron trichloride, silicon tetrachloride, phosphorus trichloride, phosphorus oxychloride, mixtures thereof, and the like.

As will be understood by those skilled in the art, what has been described is the preferred embodiment of the invention; however, many modifications, changes and substitutions can be made therein without departing from the scope and the spirit of the following claims.

What is claimed is:

1. A process for halogenating a rare earth-fluorine compound which comprises: establishing a heated reaction zone, said zone containing a particulate rare earthfluorine compound, providing said heated reaction zone with a fluorine acceptor selected from the group consisting of at least one of boron, silicon, germanium, phosphorus, arsenic and antimony, and a halogen selected from the group consisting of at least one of chlorine and bromine, and heating the resultant admixture for a period of time suflicient to convert at least the major portion of the rare earth values in said compound to water soluble rare earth halides.

2. A process for halogenating a rare earth-fluorine compound which comprises: preparing an intimate admixture comprising a particulate rare earth-fluorine compound, a fluorine acceptor, the fluoride of said acceptor being volatile at a temperature below about 800 C., and a halogen selected from the group consisting of at least one of chlorine and bromine, heating said admixture to a temperature sufficient to produce a rare earth halide selected from the group consisting of at least one of rare earth chloride and rare earth bromide but below the sintering temperature of said admixture, for a period of time sufficient to convert at least a major portion of the rare earth values in said rare earth-fluorine compound to said rare earth halide.

3. A process for halogenating a rare earth fluocarbonate ore which comprises: preparing an intimate admixture comprising a particulate rare earth fluocarbonate ore, a fluorine acceptor, the fluoride of said acceptor being volatile at a temperature below about 800 C., a halogen selected from the group consisting of at least one of chlorine and bromine, and an oxygen scavenger, heating said admixture to a temperature sufficient t produce a rare earth halide selected from the group consisting of at least one of rare earth chloride and rare earth bromide but below the sintering temperature of said admixture, for a period of time sufficient to convert at least a major portion of the rare earth values in said ore to said rare ear h ides.

4. A process for halogenating a rare earth fluocarbonate ore which comprises: establishing a heated reaction zone, said zone containing a particulate rare earth fluocarbonate ore, providing said heated reaction zone With a fluorine acceptor, the fluoride of said acceptor being volatile at a temperature below about 800 C., an oxygen scavenger selected from the group consisting of at least one of carbon and carbon monoxide and a halogen selected from the group consisting of at least one of chlorine and bromine, and heating the resultant admixture for a period of time suflicient to convert at neast the major portion of the rare earth values in said ore to water soluble rare earth halides.

5. A process for halogenating a rare earth fluocarbonate ore which comprises: establishing a heated reacted zone, said zone containing an intimate admixture of particulate carbon and a particulate rare earth fluocarbonate ore, providing said heated reaction zone with a fluorine acceptor, the fluoride of said acceptor being volatile at a temperature below about 800 C., and a halogen selected from the group consisting of at least one of chlorine and bromine, and heating the resultant admixture for a period of time suflicient to convert at least the major portion of the rare earth values in said ore to water soluble rare earth halides.

6. A process for chlorinating a rare earth fluocarbonate ore which comprises: establishing a heated reaction zone, said zone containing an intimate admixture of particulate carbon and a particulate rare earth fluocarbonate ore, providing said heated reaction zone with a fluorine acceptor, the fluoride of said acceptor being volatile at a temperature below about 800 C., and chlorine, and heating the resultant admixture for a period of time suflicient to convert at least the major portion of the rare earth values in said ore to rare earth chloride.

7. A process for brominating a rare earth fluocarbonate orew hich comprises: establishing a heated reaction zone, said zone containing an intimate admixture of particulate carbon and a particulate rare earth fluocarbonate ore, providing said heated reaction zone with a fluorine acceptor, the fluoride of said acceptor being volatile at a temperature below about 800 C., and bromine, and heating the resultant admixture for a period of time suflicient to convert at least the major portion of the rare earth values in said ore to rare earth bromide.

8. A process of producing rare earth chloride which comprises: preparing an intimate admixture of a particulate rare earth-fluorine compound and boron trichloride, heating said admixture in a heated reaction zone for a period of time suflicient to convert a major portion of the rare earth values in said compound to rare earth chloride.

9. A process for recovering rare earth chloride from a rare earth-fluorine compound comprising: :treating a rare earth-fluorine compound with chlorine, carbon monoxide and silicon tetrachloride at a temperature between about 500 C., and about 750 C., for a period of time sufficient to convert at least the major portion of the rare earth values in said compound to rare earth chloride.

10. A process for recovering rare earth chloride from a rare earth-fluorine compound comprising: treating a rare earth-fluorine compound with chlorine, carbon monoxide and silicon dioxide at a temperature between about 500 C., and about 750 C., for a period of time suflicient to convert at least the major portion of the rare earth values in said compound to rare earth chloride.

11. A process for producing rare earth chloride comprising: preparing an intimate admixture of particulate carbon and particulate rare earth fluocarbonate ore, heating said intimate admixture to a temperature between about 550 C., and 750 C., contacting the resultant heated admixture with phosgene and silicon tetrachloride to produce rare earth chloride, and recovering rare earth chloride.

References Cited UNITED STATES PATENTS 3,075,901 1/1963 Hulter et al 2387 X CARL D. QUARFORTH, Primary Examiner. S. TRAUB, R. L. GRUDZIECKI, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,353,928 November 21, 1967 Mark M. Woyski et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 18, for "chlorates or bromates" read chlorides or bromides Signed and sealed this 18th day of February 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR HALOGENATING A RARE EARTH-FLUORINE COMPOUND WHICH COMPRISES: ESTABLISHING A HEATED REACTION ZONE, SAID ZONE CONTAINING A PARTICULATE RARE EARTHFLUORINE COMPOUND, PROVIDING SAID HEATED REACTION ZONE WITH A FLUORINE ACCEPTOR SELECTED FROM THE GROUP CONSISTING OF AT LEAST ONE OF BORON, SILICON, GERMANIUM, PHOSPHORUS, ARSENIC AND ANTIMONY, AND A HALOGEN SELECTED FROM THE GROUP CONSISTING OF AT LEAST ONE OF CHLORINE AND BROMINE, AND HEATING THE RESULTANT ADMIXTURE FOR A PERIOD OF TIME SUFFICIENT TO CONVERT AT LEAST THE MAJOR PORTION OF THE RARE EARTH VALUES IN SAID COMPOUND TO WATER SOLUBLE RARE EARTH HALIDES. 